The present invention relates to an internal combustion engine.
German Patent No. 196 00 566 Cl discloses a multicylinder internal combustion engine whose cylinder crankcase is provided with an oil cooler for lubricating oil. The oil cooler is located in an integrally cast water tank on the side of the cylinder crankcase with cooling water from a cooling water circuit flowing through it. The cooling water flows around the oil cooler and is then sent into the cylinder head where it flows along the outside of the cylinder as a cooling water jacket.
A disadvantage of this design is that the lubricating oil has a high viscosity because of the low temperatures when the internal combustion engine is cold, e.g., in startup after a relatively long standstill, and because of its reduced flow capacity it is not capable of adequately lubricating the moving parts of the internal combustion engine, in particular the bearing points of the crankshaft and the connecting rod.
Another problem with a cold engine is that fuel condenses on the cylinder walls, so the fuel/air ratio in the combustion chamber deviates from the optimum, and the pollutant concentration in the exhaust is increased.
To avoid this problem, German Patent Application No. 29 05 571 proposes that the cooling water be preheated with the help of an electric heating element, so that heated cooling water flows around the cylinders and preheats them. This measure should make the engine much easier to start and should also prevent frost damage. However, the problem that arises here is integrating the heating element into the cylinder crankcase in such a way as to achieve a compact design of the device while also yielding the possibility of retrofitting with little outlay older internal combustion engines whose cylinder crankcase is not prepared to accommodate a heating element and nevertheless being a device with a small design.
An object of the present invention is to improve upon the cold start properties of an internal combustion engine, where the required measures should be feasible without increasing the size of the installation space and subsequent retrofitting should be possible.
The present invention provides an internal combustion engine with an oil cooler arranged in a water tank of a cylinder crankcase, with cooling water from a cooling-water circuit flowing through the water tank. The present invention is characterized in that an electric heating element is provided which is arranged in the water tank.
The electric heating element can also be installed in the water tank subsequently without requiring extensive conversion measures, and the crankcase in particular need not be altered. This yields a fully integrated cooling water heating system which can be operated to preheat the engine even before starting and greatly improves the startup properties and contributes to pollution reduction. The cooling water heating system requires practically no additional installation space and can be installed easily and directly even later at the customer""s, thereby lowering installation costs. Maintenance work can also be performed quickly. Costs are reduced on the whole, because the crankcase need not be converted.
Another advantage is that the lubricating oil is also heated due to the position of the oil cooler directly on the heating element or in the water tank which is flooded with cooling water that has been heated, so this improves the flow properties. The lubricating oil flows more readily to the bearing points, thus yielding better lubrication of moving parts. The heated oil cooler in turn influences the cooling water, because the cooling water is heated more quickly due to the increased radiant heat surface of the oil cooler, so the cylinders are also preheated in a shorter period of time.
The heating element and the oil cooler preferably form a composite element by having the heating element mounted directly on the oil cooler, in particular by soldering onto the bottom of the oil cooler. This yields a cohesive component of heating element and oil cooler in a space-saving design that can be prefabricated in particular and installed in the water tank and can be removed from the water tank for maintenance work.
According to a preferred embodiment, the heating element is designed as a heating coil, so the heat radiating surface area of the heating element is increased and the heating process is carried out in a shorter period of time.
The heating element is advantageously located completely inside the lateral border of the bottom of the oil cooler, so the dimensions of the water tank can remain essentially the same and in particular the installed height of the cylinder block remains the same; this yields an especially space-saving design.